Thanks in large part to wind and solar energy, not only have German electricity prices paid by consumers skyrocketed over the past years, thus casting a large number of homes into home fuel poverty, but also the supply itself is rapidly becoming precarious and unreliable.

One problem is the stabilization of the power grid in the face of wildly fluctuating wind and solar energy feed-in. The other problem is the mechanical integrity associated the wind turbines themselves. Hat-tip: Gerti Brunthaler at Facebook.

Catastrophic wind turbine failures

Increasingly it is becoming apparent that wind turbines have a way of just collapsing – often without notice – due to mysterious causes. One might suspect mechanical fatigue due to the complex cyclic loading that wind turbines are subjected to. Consequently wind parks are becoming hazardous zones for persons and property in the vicinity – never mind the proven detrimental health effects of infrasound.

One example (of many) of a recent catastrophic turbine failure is reported by the North German Ostesee Zeitung here. According to the article, just 2 days ago, the blade of a wind turbine snapped off unexpectedly, boring itself into the ground. The Ostsee Zeitung writes that local residents were “shocked” and the reason for the collapse is unknown. The online news site writes:

At the time of the accident there was neither a storm nor unusual weather conditions. ‘We are baffled as well,’ says Carlo Schmidt, Managing Director of Windprojekt company, which operates the turbine in question.”

Forestry machinery operator Erik Karlsson of the Vetlanda municipality heard an “incredible bang” while working on Christmas Eve, but thought nothing of it. Later as went home he discovered that a nearby wind turbine had fallen to the ground across the road. The huge turbine mast had snapped some 15 meters up and the unit came crashing down, the SVT writes. Authorities quickly cordoned off the wind park area. Here as well the cause of the failure is unknown. The wind park has since been designated as a hazardous area: “The public has been asked to keep away.”

These are just two recent examples of many of wind turbine collapses.

Blackouts to prevent blackouts

In addition to catastrophic mechanical failures, wind and solar energy are wreaking havoc on power grid stability, so writes the German online mittelhessen.de here.

The online newssite reports that the future for the residents of Wetzlar may be looking bleak. Why?

If in the future the power goes out, the reason maybe rooted in the energy management act. In order to eliminate the possibility of widespread blackouts, grid operators such as Enwag are obligated to switch off consumers or even entire parts of the city.

These targeted blackouts are necessary, mittelhessen.de writes, because it is the only way left to keep the power grid from over or under-loading. The site tells readers:

The probability of large blackouts is increasing with the strongly growing power generation from wind and sun. Experts have long seen the power grid threatened by this.”

Unfortunately grid operators will have to react very quickly to the power grid fluctuations. The mittelhessen.de reports that “there won’t be any time for operators to make long calculations” and that “there will be only an hour to react”. Just how vulnerable is the power grid in the Wetzlar region? Mittelhessen.de writes:

A chain of seemingly harmless single incidents can in the worst case lead to a domino effect and lead to outages in all connected power networks.”

In plain English: one small problem could lead to a widespread blackout. To keep this from happening, the solution is now to conduct targeted blackouts in an attempt to keep the grid balanced. If you are running a company, or merely working on an important document at your PC, then it’ll just be tough luck. Just use paper and pen, and light up a candle.

Junk energy at a high price. Other countries may wish to think twice before copying the model.

“Junk energy at a high price. Other countries may wish to think twice before copying the model.”

Looking at our daily news, it would seem we don’t have the time to think because we are busy running down the same dead end street. Junk government always comes at a high price and there is no doubt we will pay. So much for the bad.

Now for the good:

Pierre, your daily hard work is among the finest forms of serving your fellow man. I pray and hope that you efforts succeed and keep changing public opinion. It is already a matter of life and death for hundreds of millions of the poorest in many parts of the world, and increasingly so in our own countries. Thank you for caring as so many coldly turn away. I wish you good health, and the strength and stamina to get up every day to deal with the deluded, stupid, opportunistic or just plain evil. It takes a strong and good man to keep faith and carry on.

Pierre, may I offer support of the words of Colorado Wellington. Thanks Colorado for saying it so well.

Pierre, you are indeed one in a million, and you are doing a very important thing with your blog. May 2016 go well for you. Take care of yourself, and may you be be blessed with happiness, health and prosperity … and more great blogging.

First: I’m amazed to hear a tower can be built close enough to fall across a road that can be used by people other than those associated with the facility. Maybe it is just that there is more open space in my region so the need is less here.

Second: Just as the tires on a car need to be “balanced” with tiny weights, the blades of a wind machine have to be balanced or else the rotor is going to have an early demise. This is a serious issue for large spinning things.
Also, because they are so large the “wind load” on the blades can be different from side to side or from top to bottom. Wind does not have a uniform cross-section. This is easily seen where there are tree leaves on the ground or loose in the air. They don’t all move at the same time, in the same direction, or at the same rate. The many possible unbalanced forces are relentless.

Contrast the above with any other spinning machine that has to be reliable over a long service life. A big hydro power plant will have rows of turbines, all finely balanced and otherwise tuned to very small tolerances. Think of a jet engine on a big plane. They can’t be allowed to self-destruct.[ Rotor Balance ]

Pierre:
A Happy New Year to you and your loved ones. And to all readers, even sod.

Thank you for a great blog and your efforts.

I am not sure why steel towers should crack – that is an engineering design problem possibly caused by scrimping on the steel.
As for the blades, these are polyester/fibreglass and the composite is prone to cyclic stress fatigue. The life will depend on the type of polyester resin used, on the grade of reinforcement, the construction and especially the strength of the stress.
Normal laminates (standard polyester resins) can fail in a little as 1,000 cycles, so those used in turbine blades are formulated for better flexible strength and toughness. There are better resins but these are more expensive. When laminates start to fail the fault can propagate through the laminate faster than the speed of sound, hence the loud crack sound and speed of failure.
Carbon fibre is strong, it is also brittle so it isn’t the answer. The turbine blades are usually based on boat construction methods using what is known to have worked, but this ignores the increased frequency of the stresses in the blades. De-lamination between the layers is likely also. This will be fixed over the next 20 years as experience enables the engineers to design blades that are safer, but also requires less input into the design from accountants, salesmen and politicians i.e. those who know nothing about design but like to interfere. Whether anybody wants to buy turbines in 20 years is another story.

The problems with blades have been known for more than 30 years!
And I’m puzzled why they haven’t moved on to metals for the large blades instead. Not as “sexy”?

And while it’s easy to say that somebody’s been scrimping on the steel, there are still vast unknown in terms of the nominal loading on the tower structure. Structural Engineers may not immediately recognize that they are supposed to be designing a support for a rotating machine that can slew and has cyclic loading; which operationally also influences the wind loading on the tower itself. A quasi-stable design method seems to prevail. With larger safety factors applied, but not knowing if those factors are appropriate, effective or efficient.

Although computer design methods and multi-physics analysis methods such as FOAM (Field Operation And Manipulation) are available; the aerodynamics of the blades isn’t well known except under laminar flow conditions. Conditions that only exist when turbines are well-space: at 10 to 20 rotor diameters; not the typically 3 to 5.

Beyond designing the tower (with everything attached) not having a resonant frequency or harmonic coinciding with e.g. blade-passing frequency, there is little routinely done in terms of dynamic analysis.

30 years ago, when tasked with designing a support tower for a wind turbine; I was left with an ocean of unknowns and uncertainties. Suppliers of generating gear and the blades could tell me nothing of much use beyond the nominal mass and overall dimensions. Major loads had to be estimated. With limited computing power at hand and little time there was no option but a quasi-static analysis and a memo to the chief Engineer about the many unknown factors which could not be allowed for in the design because of a lack of information. The customer never saw that memo.

Because of the unknowns, the structure shouldn’t have been built. It was. It failed. It began to fail early.

There seems to have been little if any progress in the Engineering of such things, despite (because of?) decades of subsidies. Just doing the same thing, over and over again; expecting a different result. 🙁

The blades are actually ‘hollow’ in most of their length, with laminates and probably an interior layer of ‘foam’ making each skin. Around the hub more strength is built in with heavier (thicker) laminates and probably different ‘spacing’ material e.g. end grain balsa blocks. Failure of any of these joins may lead to overall failure.

The mass of a metal blade need not be substantially higher. Increased rotating inertia reduces the torque pulse as the blade passes the tower. The advantage of metal is more controlability of the material’s strength.

Deflection is not a problem; it’s calculable. A good design might use the deflection under load to “spoil” the airflow without any mechanism needed at the limit to “feather” the blades in e.g. a storm.

High strength and stiffness is, AFAICT, really only available with composites when the whole item can be autoclaved and baked. That’s not cheap. And it’s energy intensive. When composites are joined by dissimilar materials (e.g. steel bolts), the distribution of stress and strain has to be carefully engineered.

Ingrained practices tend to make people build things the way that they used to. Metals; especially light alloys have changed a lot in 30 years. There are metal-glass composites (e.g. GLARE) that are vastly more tear resistant and stiffer than polymer or carbon fibre composites by themselves. They don’t get used to make wind turbine blades, even though the material is de rigueur in the aerospace industry.

Manufacturing methods change much more slowly when there’s little competitive pressure; and subsidies are available to harvest regardless of performance.

Aluminium has one that is independent of load. Use an aluminium tennis racquet for a while and you’ll probably meet this.

Steel has one but usually can be ignored at light loads. Which might not be the case here given the unknowns that Bernd mentions

2. Stress cracking in composites.

Composite sailplanes met a new frontier in Australia with crazing of the gel coat that was found to progress into the rest of the structure. GFA had wings flexing in a test rig to explore this at one stage

Ian;
thank you for the link. I note specifically he commented on an epoxy laminate but the same would apply to polyester one. Once the gelcoat cracks the underlying laminate is exposed to UV and water. Both can cause deterioration in the laminate, and flexing would make it worse.

UV at altitude (e.g. central Australia) can craze perspex (acrylic) in 12 months, whereas it is usually OK outdoors for 10 years. UV initiates cross-linking of the resin, which makes it more brittle hence damage from flexing.

I might comment that there are better gelcoats than in the mid 1980’s but they aren’t much better for flexing structures. The top finishes used on commercial and military aircraft are 2 pack polyurethanes known (and specified) as lasting 5 years. Partly composition also the basic resin is very flexible. The only problem is the toxicity which means it has to be applied industrially, not on the airfield. Bernd Felsche refers above to auto-claving as used for higher strength esp. epoxies and polyurethane can be applied as an in-mould coating which would replace gelcoat.

As I recall the real problem was the crack continuing into the structure below the gel coat. The question was “would it continue through the glass fibre?” – of major concern when it is in a wing spar! Hence the flexing testing.

I’ve been away from gliding and the airworthiness side too long to point you directly to the result – I found a mention of AN 69 Issue 3 but can’t find a link. It will be somewhere in the GFA AD list I’m guessing butthat is pretty long.

A further vote of thanks for all your efforts during 2015 – keep up the good work!

As to the stresses suffered by turbine blades – I operated an open cockpit ultralight for some 20 years, flying from a small airstrip about 5 miles from the North Sea Coast. As such I am acutely aware of how the wind speed, direction & temperature can change dramatically in the first few hundred feet above ground level. Inversions are quite common in that sort of area, and I remember many occasions when I took off into a chilly easterly wind, yet suddenly climbed through an inversion into a much warmer westerly (typically at 500ft). Now imagine a large turbine blade in this situation – it will start off encountering an increasing force as it rises from the bottom of the arc. Then, as it reaches the upper third, it will suddenly experience the higher temperature, and simultaneously the opposite wind direction. This stress reversal will move along from the tip towards the hub, and then back again as it falls down the other side of the arc. Now imagine the effect this will have when repeated for long periods. Is there any proof that this scenario is allowed for by the designers, if indeed it can be considering the comments by Graeme No.3?

O/T We all think of Greens as hair-shirt-wearing vegan bicyle-riding anti-consumerist killjoys. But nothing could be further from the truth.
New German poll finds, Green voters are more likely to use airplanes than socialist and “conservative” (CDU) voters, AND: 58% of them endorse that flying is affordable to nearly everyone! 86% of them think that a good airline network is important for Germany!http://www.mmnews.de/index.php/politik/61826-2016-01-01-05-58-59
Conclusion: Got some new shiny black plastic toy? Sell it to the Greens!

Probably not surprising for anyone who’s watched the watermelons evolving from the 70s till today. They have always seen themselves as the moral and intellectual elite so why should they be deprived of the rewards? This fits the pattern. I think the gap is actually bigger with many people lying to look more “virtuous”. Also, by definition, the answers show what people say they do or support rather than what they actually do or want.

And concerning the affordability of flying? New York film critic Pauline Kael described the phenomenon over 40 years ago when she commented on Richard Nixon’s “surprising” victory:

“I live in a rather special world. I only know one person who voted for Nixon. Where they are I don’t know. They’re outside my ken. But sometimes when I’m in a theater I can feel them.”

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